Today, while looking for something else, Eli came across the answer to another question, where does the CO2 come from. Over the years there has been a fair amount of discussion about why measure CO2 on Mauna Loa or the South Pole, or Barrow Alaska, or the other places where it is measured. Another strand we have seen the denialists use as a thin comb over is that China should cut its emissions first, and, of course that evergreen that North America (they always say the US, swallowing Canada) absorbs more CO2 than it emits.

AIRS is the Atmospheric Infrared Sounder on the Aqua satellite. Originally designed to measure water vapor (why do you think it is on Aqua), it has a ~2500 element IR spectrometer. Relatively recently NASA has figured out how to use this to measure CO2 in the atmosphere.

This is a mid-troposphere image at 8 km. Simon Donner has a recent series of posts on CO2 emission intensities but this figure is worth a thousand posts (even Simon's:) Clearly the two most intense sources are the east and west coasts of the US. While there is a region of higher emissions to the west of China, it is much weaker than that from the US. In the southern hemisphere there is a band that passes through the River Plata area (Buenos Aires, South Africa and the more settled parts of Australia. The data is available, and we can look forward to the movie (starting in 2002).

18 comments:

Because, as you correctly point out, Rabetts don't read. I had just gone through a bunch of information on the measurments and mid-trop was in my head, and mid-trop is a range, 5 km included and often used. There is also the issue that the height of the troposphere varies with latitude, so it would technically be better to use a pressure , e.b. 500 hPa, but that is just an excuse. My bad. It has been corrected.

Thank you. I suspected something of the sort (having misread plenty of pictures myself). As for pressure, I think that is better only if the detection method itself is pressure dependent - that is, if the method used to extract co2 data from AIRES data works only over a range of pressures (which seems likely, but I can't seem to find any statement of this), then then it would be ideal to give the range of pressures. But if the method is only dependent on absolute altitude, altitude would be ideal.

I love that map but wish I understood it better. As Prof R. himself instructed me in the ways of lowtran, he no doubt knows that CO2 is very opague where it is opague, and consequently it takes a careful choice of frequencies to probe very far down in the atmosphere. It would be nice to know what the contribution fucntions of the available lines looked like so we could tell at what height that CO2 really is.

Is it a little odd that the strongest CO2 emissions are so far displaced from their apparent sources? Clearly, prevailing weather and climate have an influence. It's actually not obvious that China is a weaker emitter than the US, and most estimates say it isn't. There is more than one such oddity - why, for example, does Brasil not seem to be emitting anything? Is the rainforest an explanation or is it just the global circulation pattern? I'm going to guess that the latter is more important.

Anonymous 7:19- I thought that as well, then some googling suggested that the Jet stream was higher up, but that there were winds and suchlike moving things around at the 8km height. So I suspect it is a mixture of various winds including the jet stream, but precisely what I do not know.

There are - of course - a lot of caveats in sattelite based CO2 observations. Because if there weren't we should already have them available. The biggest caveat is that a CO2 spectrometer cannot see through clouds, and that the small annual human imprint - in particular on land - is overwhelmed by the natural annual co2 variabiliy, which has to be modeled and substracted.

The 8 km altitude CO2 image thus shows predominantly the result of mixing in the hadley cell, which in july is already al lot of forest fires.

I can understand forest fires having some importance in some parts of the world, but not right across the mediteranean and Atlantic oceans, Italy, Iran and into central Asia, including what looks like the Gobi desert.Certainly the data here is of limited usefulness.

The map reflects the sinks too. Notice lower concentrations east of the Mississippi and the Pacific NW, where there are expansive forests.

Keep in mind, when I write about "emissions intensity", I'm referring to emissions/GDP. Even if the map showed the same level emissions (ignored sinks for a moment) from China, as from the US, the emissions/GDP is still much lower in China. Right now, at least, North America's economy is more carbon efficient (more GDP per ton of GHG emissions).

The pattern for the western US might be consistent with fires -- though there are also a lot of power plants located in the Intermountain West, but I'd guess that the pattern along the eastern seaboard is probably not due to fires. Much more likely to be related to emissions from power plants.

I don't know about the pattern in Europe, but I expect it is also more likely not due to fires.

As has been pointed out above, the pattern does not match the source because the sources are lower than the sampling elevation and the CO2 gets moved around by prevailing winds so by the time it gets high enough to be sampled, it is no longer above the point of emission.

If memory serves, the intermountain (that is, between the rockies and the sierra nevadas west in the US is disproportionately coal-powered, has a high proportion of truck and train shipping, and relatively high vehicle-miles per person.

So the entire scale of the color map is about 16 or 17PPM. What is the accuracy of the measurement itself? Also, I would imagine that at 26K feet, most of what you are measuring must be from hundreds of miles uprange. How, then, do you explain these readings? What was the synoptic pattern at the time of measurement?

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Eli Rabett

Eli Rabett is a not quite failed professorial techno-bunny, a chair election from retirement, at a wanna be research university that has a lot to be proud of but has swallowed the Kool-Aid. The students are naive but great and the administrators vary day-to-day between homicidal and delusional. His colleagues are smart, but they have a curious inability to see the holes that they dig for themselves. Prof. Rabett is thankful that they occasionally heed his pointing out the implications of the various enthusiasms that rattle around the department and school. Ms. Rabett is thankful that Prof. Rabett occasionally heeds her pointing out that he is nuts.